Defining Views

Views are relations, except that they are not physically stored.

They are used mostly in order to simplify complex queries and

to define conceptually different views of the database to different

classes of users.

View: purchases of telephony products:

CREATE VIEW telephony-purchases AS

SELECT product, buyer, seller, store

FROM Purchase, Product

WHERE Purchase.product = Product.name

AND Product.category = ‘telephony’

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